Vacuum tube base pin



A. W. MINER VACUUM TUBE BASE PIN Nov. 21, 1933- Filed Jan. 12, 1929 9 villi 117:!!!vllvlllilflilllilt .Iilllllr'l Ill 1 ZIIIIIIIG Willi!!! Fly/5; 259/61 aktozmqs Patented Nov. 21, 1933 1,936,404 I VACUUM TUBE BASE PIN Anson W. Miner, Waterbury, Conn., assignor to The Waterbury Brass Goods Corporation, Wa-

terbury,

Conn., a corporation of Connecticut Application January 12, 1929. Serial No. 332,138

8 Claims.

This invention relates to contact pins for vacuum tube bases, and has for an object to provide an improved construction of seamless pin made of drawn sheet metal or metal tubing.

3 It is also an object of the invention to provide a contact pin which has maximum strength for the amount of material used, which will be so constructed that an indefinite number will be made of uniform dimensions and finish, and in which the walls are of uniform thickness throughout.

With the foregoing and other objects in view, I have devised an improved pin construction and method of making the same as illustrated in the accompanying drawing. In this drawing,

Fig. 1 is a section through a vacuum tube base and a pair or" contact pins applied thereto, and showing how the lead wires are secured to the cm.

Fig. 2 is a top plan view of a blank showing the first step in the manufacture of these pins from sheet metal.

Figs. 3 to 8 illustrate the various steps in shaping and drawing the blank to bring the blank to 25 the proper size and length for the final operation of forming the flange.

Fig. 9 is a section through dies shown somewhat diagrammatically for forming the flange or bead in the open position before the head is formed.

Fig. 10 is a similar view showing the dies closed and the bead formed.

Fig. 11 is a top plan view and longitudinal sec tion of one form of finished pin of the larger size.

Fig. 12 is a top plan and longitudinal section of a slightly difierent form of pin used mostly for the smaller size.

Fig. 13 is a partial longitudinal section and partial side elevation showing the bead or flange 40 formed at one end thereof.

Fig. 14 is a longitudinal section of a pin open at both ends.

Figs. 15 and 16 show the lower open ends of pins in section indicating the different shapes which may be given to these pins, and

Fig. 17 is a section of mold shown somewhat diagrammatically indicating how my improved pin may be mounted in the vacuum tube bases.

In the manufacture of vacuum tubes the glass bulb and the inner parts of the vacuum tube are made and assembled and the bulb sealed. The lead wires connected with the inner parts, such as the filament, plate and grid protrude from the small end of the bulb, which small end is insorted in and secured in a cup shaped base usually of molded insulated material in which the contact pins are mounted, and these protruding wires are soldered to the respective pins to provide the electrical contact or connection with the sockets of the radio set. The contact pins are made and then either molded into the insulating base as it is made, or the base is first molded with openings for the pin and then the pins are staked into the base by being thrust into the openings in the base and their inner ends expanded to lock the pins in the openings. After the pins are properly mounted in the base, the end of the bulb carrying the projecting wires is inserted and the wires soldered to the proper pins. A com mon construction of vacuum tube requires four pins, two large pins and two small pins, but there are vacuum tubes having more pins, 2. later form having five oi the smaller pins.

Contact pins have heretofore been manuiac tured from solid brass rod stock by turning and drilling in an automatic screw machine, and as they required flanges for properly anchoring the pins in the base it will be obvious their manufacture required the turning oif of considerable metal. Also as they were required to be drilled longitudinally the walls were apt to be nonuniform in thickness as due to inaccuracy of the machine or wear the bore of the pin would not be accurately centered. Furthermore, if the pins were molded into the base of a vacuum tube at the time the base was molded the inner ends of these pins were left closed to prevent entrance of the molded material into the pins and these ends had to be later drilled for passage of the wires before they were soldered to the pins. will be obvious that this method of making pins and assembling them is a relatively exp sive one and it was, furthermore, liable to produce pins which were not uniform.

Another type of pin has been constructed oi sheet metal which was rolled up from a flat piece of metal into a tube with a lengthwise seam and was then beaded. When these sheet metal pins were used the bases were molded with holes for the pins and the pins were then staked in the holes. When so staked some of the pins were liable not to be rigidly secured, and therefore, were not absolutely rigid as they should be in the holes. Some of these sheet metal pins may also have been molded in the bases, but they are not considered safe to use as some provision had to be made to prevent them filling up with the composition during the molding and even then there is danger of the seam opening up and allowing the composition to be forced into the tube and devised an improved method of making it. This pin may be drawn of seamless sheet metal or made of tubing and may have either a straight end as shown in Fig. 12, or beveled end, as shown in Fig. 15, or rounded, as shown in Fig. 16, or the open end may be turned in, as shown in Fig. 11. It has many advantages over the turned pin or the rolled up sheet metal pin above described.

It may be made either closed atone end, as shown 'in Figs. 11, 12 and 13 if it is to be molded into the base, or it may be made open at both ends, as shown in Fig. 14, if the user desires to stake the pins in the molded base instead of molding them in.

In making these pins from sheet metal a circular blank 20 is blanked from sheet metal of the proper thickness. This blank is then drawn in suitable dies to the proper length and diameter, the various steps in this drawing operation being shown in Figs; 3 to 7 inclusive. After the tube is properly drawn the open flared end 21 may be trimmed oif leaving the tube the proper length for forming the bead or flange, the blank being new as shown in Fig. 8. Or this tubular blank may be formed by cutting off a proper length of metal tubing. It will be understood ,that Figures 2 to 8 inclusive are of a somewhat smaller scale than Figs. 11 to 16.

In forming the bead or flange 22 on the blank 23 the blank is confined both inside and out by a set of tools or dies with the exception of the portion where the head is to be formed, which portion is unconfined on its outer side. This is shown in Figs. 9 and 10 in which the die comprises two blocks 24 and 25 which are movable toward and from each other, the lower die having a socket to receive one end of the tube, which is the closed end if the tube is of a closed type, and the other die 25 has a longitudinal opening to receive the blank 23. The opposed faces of both dies are cut away or recessed about the openings, as shown at 26, of a size and shape to correspond with the size and shape desired for the bead. A pin 27 is inserted in the open end of the blank 23 to confine it on the inside. Then the dies 24, 25 and 28 are forced together subjecting the tubular blank to a lengthwise pressure. As the blank is confined except at the cutouts 26 the wall at this point is forced outwardly. In other words the sides of the blank bulge outwardly and are folded and pressed together, as indicated in Figs. 11 and 12, to form a bead 22 of uniform thickness about the tube. This bead may be formed at any point in the length of the tube either intermediate the ends thereof, as shown in Figs. 11, 12 and 14, or it may be formed at one end, as shown in Fig. 13.

These pins can be molded in the insulating base 29 of the vacuum tube or they may be staked in if desired. It is preferred, however, to mold them in as this is cheaper and they are more firmly secured. The molding of the insulating base is done under considerable pressure in suitable dies indicated somewhat diagrammatically at 30 and 31, Fig. 1'7. The lower (1 91 member of the mold 31 has suitably located openings 32 to hold the pins in proper position, and it will be obvious that as the molding is done under considerable pressure there is a tendency to force the composition down into the holes in the molds in which the pins are inserted.

If this occurs the pins stick in the holes and the molded bases are broken when an attempt is made to remove them from the molds. To further reduce this tendency the holes 32 for the pins are sometimes counterbored, as shown at 38, and the lower edge of the bead 22 forced into the recess thus formed. It will, of course, be understood that in molding the tubes in the bases the closed end 34 is within the mold to prevent the composition being forced into the pins. After the pins are molded in the bases these closed ends may be drilled for the passage of the lead wires 35 which are soldered to the lower ends of the pins, as indicated at 36 and 37, or the closed ends may be pierced in the dies as described a little later. In assembling the base on the glass bulb the lead wires are inserted in the pins and cut oil at the lower ends and then dipped in moiten solder. the opening is of sufiiciently small diameter to retain the required amount of solder by capillary action, while in the larger pins, indicated at 39,

In the smaller pins, indicated at 38, A

this capillary action is not generally suilicient.

The lower end of this tube is, therefore, turned inwardly, as shown at 40, to provide a sufliciently small opening so that the solder will be retained.

In molding the bases with the seamless pins it is possible to mold the base and pierce the closed end of the pin at the same time. In this operation the upper member 41 of the mold may carry pointed pins or plungers 42 arranged in alignment with the contact pins 38 and 39 in the lower member 31. These plungers can be so arranged that as the composition softens under the action of heat in the molding operation the decrease in resistance allows the plungers to suddenly drop and pierce the closed ends 34 of the contact pins. At the same time the tapered pointed ends of the plungers spread out the ends of the pins, as shown at 43, Fig. 1 to thus securely anchor the pins in the'base when it hardens. During this spreading action the ends of the plungers prevent the composition fiowing into the pins. Also the beads on the pins effectively seal the pin holes in the die block 31 and prevent the composition entering these holes.

These strong seamless pins have a decided advantage over both the turned pins and the rolled up sheet metal pins having a longitudinal seam. The piercing operation as described does away with the necessity of drilling the pins. These seamless pins are stronger than the turned pins or the pin of the longitudinal seam for the same dimensions and thickness. The walls of the seamless pin are of uniform thickness throughout where there might be considerable variation in the turned pin, and the rolled up pin with the longitudinal seam always has the danger of opening up in the molding operation permitting composition to escape or get into the inside of the pin which, of course, would, therefore, interfere with the connection of the lead wires. These seamless pins have a smooth uniform outer surface and as a whole have a better finish than either the turned or rolled up pin. In the rolled up pin with the longitudinal seam the seam is always liable to hold some finishing acid or solution or hold some soldering solution which might afterwards cause tarnishing or corroding of the goods,

' the turned pin.

Having thus set forth the nature of my invention, what I claim is:

l. A rigid tubular contact pin for vacuum tube bases and the like ,comprising a drawn metal seamless tube open at one end and closed at the opposite end, said tube having continuous unbroken circular side walls and having an outwardly extending circumferential bead adjacent the closed end thereof.

2. A terminal contact insert'of generally tubular form drawn from ductile sheet metal and having a central hole extending from the outer end thereof and having a thin integral wall completely closing the inner end of the central hole.

3. A contact pin for vacuum tube bases comprising a rigid member drawn from a flat metal blank as a seamless tubular member having continuous unbroken side walls, and having an outwardly extending integral upset circumferential bead on its outer wall.

4. A contact pin for vacuum tube bases comprising a rigid member drawn from a flat metal blank as a seamless tubular member, said tube having continuous unbroken side walls and an upset outwardly extending circumferential bead on its outer wall, said tube having an opening at one end and an integral cross wall at the other end.

5. A contact pin for vacuum tube bases comprising a rigid member drawn from a fiat metal blank as a seamless tubular member having continuous unbroken side walls and an upset external circumferential bead comprising outwardly extending integral walls of the tube, and said tube being open at least at one end and having the side walls at this end extending inwardly so that the opening is of less diameter than the internal passage through the tube.

6. A vacuum tube base comprising a base member of molded insulating material and a contact pin mounted in said base member comprising a drawn metal, seamless, rigid tube having continuous, unbroken side walls and an upset outwardly extending bead cooperating with said molded material to hold the pin, and said pin having a tapered opening at its inner end leading to the interior of the pin.

'7. A vacuum tube base comprising an insulating base member of molded material and a contact pin mounted in said base member comprising a drawn metal, seamless, rigid tube having continuous, unbroken, circular, side walls, and an integral bead comprising outwardly extending side walls arranged side by side so that the bead comprises two thicknesses of the metal, said head being spaced from the inner end of the pin and said end of the pin flaring outwardly to cooperate with the bead in securing the pin in the base member.

8. A vacuum tube base comprising a base member of molded insulating material and a contact pin mounted in said base member comprising a drawn metal, seamless, rigid tube having continuous, unbroken, circular side walls, said tube being open at its outer end and having the side walls at this end turned inwardly so that the opening is smaller than the internal passage through the tube, said tube also having an external circumferential bead intermediate the ends thereof comprising outwardly extending integral walls of the tube arranged side by side, the

inner end of the tube being flared outwardly to cooperate with the bead in securing the pin in the base member.

ANSON W. MINER. 

